1. Field of the Invention
This invention relates to a process for producing an oxygen-containing organic compound from olefins, and more particularly it relates to a process for producing an oxygen-containing organic compound by oxidizing olefins using a platinum group complex in the presence of water and an oxygen complex.
2. Description of the Prior Art
As an oxidation reaction for various olefins which has so far been commercially carried out, there is famous Hoechst-Wacker process (Japanese patent publication Nos. 36-1475/1961 and 36-7869/1961). According to the process, a composite catalyst having Pd(2)Cl.sub.2 and Cu(2)Cl.sub.2 as catalyst components dissolved in a hydrochloric acid solution (pH: 0 to 2) has been used. Description will be made for example referring to ethylene oxidization reaction. First, ethylene is oxidized by means of divalent palladium and water to form acetaldehyde. The reaction is expressed by the following equation: EQU CH.sub.2 =CH.sub.2 +Pd(.sub.2)Cl.sub.2 +H.sub.2 O.fwdarw.CH.sub.3 CHO+Pd(0).dwnarw.+2HCl (1)
As seen from the reaction equation, Pd(2) is reduced into metallic paradium (Pd(0)) which precipitates. Thus, by making Cu(2)Cl.sub.2 coexistent therewith in a large quantity, it is necessary to oxidize and regenerate Pd(0) into Pd(2) as shown in the following equation: EQU Pd(0)+2Cu(2)Cl.sub.2 .fwdarw.Pd(2)Cl.sub.2 +2Cu(1)Cl (2)
Difficulty soluble Cu(1)Cl by-produced at that time is oxygen-oxidized in the coexistence of HCl and returned into Cu(2)Cl.sub.2 according to the following equation: EQU 2Cu(1)Cl+1/2O.sub.2 +2HCl.fwdarw.2Cu(2)Cl.sub.2 +H.sub.2 O (3)
By employing a redox system of Pd(2)/Pd(0) and Cu(2)/Cu(1) in such a manner, continuous oxidation of ethylene has been made possible, but this oxidation is not a direct oxidation of ethylene with oxygen, but an oxidation by means of Pd(2) ion dissolved in water; hence the oxidation and regeneration of Cu(1)Cl becomes a rate-determing step. Further, since the solubility of oxygen in water is low, it must be raised up and therefor the oxygen treatment has been carried out at high temperatures and high pressures such as 100.degree. C. and 10 atm. Further, in the case of higher olefins, since the oxidation rate is low to need a longer reaction time, it has been regarded that oxidation of 1-butene or higher olefins has not yet been practically carried out (Tamura, "Catalyst", 21, 167 (1979)). Still further, since a high concentration of HCl aqueous solution is used, a corrosion-resistant material such as titanium, Hastelloy (tradename of product made by Heynes Stellite Co., Ltd.) is required. Thus, the reaction has been carried out at high temperatures and high pressures as described above, so that a process capable of oxidizing olefins under mild conditions has been desired.
On the other hand, as to cyclic compounds, cyclopentanone as a representative example of ketocycloparaffins is a useful compound, since it is readily convertible into .delta.-valerolactone which, when subjected to ring opening polymerization at room temperature, yields nylon-6,10, or sebacic acid which, when subjected to its polycondensation with hexamethylenediamine, yields nylon-6,10. Cyclopentene as its raw material is contained in a C.sub.5 fraction in a mixture obtained by naphtha cracking in a high concentration in the range of 15 to 25% by weight, or it is easily obtained by partial hydrogenation of cyclopentadiene by-produced in a proportion of 2 to 4% at the time of ethylene production (see K. Weissermel and H. J. Arpe, Industrial Organic Chemistry, translated by Mitsuaki Mukohyama, Tokyo Kagaku Dohjin (1978)). Accordingly, if oxidation reaction of cyclopentene into cyclopentanone is commerciallized, this will have a great meaning.
According to a cyclopentanone production process via cyclopentene oxidization, which has so far been reported, first the reaction is carried out at a reaction temperature of 50.degree. C., for a reaction time of 2 hours in the presence of a catalyst system of palladium chloride (hereinafter denoted by Pd(2)Cl.sub.2) and ferric chloride (FeCl.sub.3.6H.sub.2 O) in ethanol solvent, to obtain the product with a conversion of 70% and a selectivity of 90%, but the reaction mechanism has not yet been known (Takehira et al, Japan Chemical Society, the 45th Spring Annual Meeting, 4G 19 (1983)).
On the other hand, it has already been reported by F. C. Phillips in 1984 that various olefins are oxidized by means of Pd(2)Cl2 in the presence of water the form oxygen-containing compounds (F. C. Phillips, J. Am. Chem. Soc., 16, 255 (1984)). As to this reaction, since such compounds are prepared in the same manner as in the case of linear olefins described above with regard to Hoechst-Wacker process, the above-mentioned problems of corrosion-resistance and reaction being carried out at high temperatures and high pressures has still been raised.
The object of the present invention is to provide a process for producing an oxygen-containing organic compound having overcome the above-mentioned problems, by oxidizing olefins under milder conditions.
The present inventors have previously proposed a process for producing acetaldehyde in a non-aqueous solution system under mild conditions, by directly oxidizing ethylene activated by complex formation, with combined oxygen activated by complex formation, in the presence of a composite catalyst comprising a transition metal complex capable of forming an oxygen complex through coordination of the transition metal with oxygen and a platinum group complex capable of forming an ethylene complex through coordination of the platinum group metal with ethylene (Japanese patent application Nos. 58-104291/1983 and 59-4180/1984).
The present invention is based on such a finding made during the above research, that the oxygen complex in the above-mentioned inventions has a capability of oxidizing Pd(0) into Pd(2)Cl.sub.2 in the presence of water with a good efficiency.